If this can help anyone, I also suffered related issues with the same symptoms and it had to do with some CF7 custom validation rules for text fields I had setup in functions.php.
One of them was not returning anything and that missing return statement was the culprit.
I am having the exact same issue on an instance I just tried updating.
My site is no longer responding because of this issue.
I previously suffered the exact same issue and this was due to TGM Plugin Activation class which I had to manually update because of a security issue.
Here are the appropriate links:
http://themeforest.net/forums/thread/unexpected-t_paamayim_nekudotayim-classtgmpluginactivationphp-on-line-1109/174232
http://themeforest.net/forums/thread/security-vulnerability-affecting-wordpress-plugins-and-themes/173011
Please fix this as soon as possible.
JP
